Why winter can affect your mood: understanding SAD

You know that feeling when October arrives, and it's like someone's turned the lights down on your life? Well, you're not imagining it. 

For some people, the shorter days don't just mean darker evenings. They mean a real, physical shift in how their brain works, and it's got a name: Seasonal Affective Disorder, or SAD for short. The name fits, too, doesn't it?

What SAD feels like

It's more than just "winter blues." SAD is your body genuinely struggling because there's less sunlight reaching your eyes and skin.

You might find yourself waking up exhausted no matter how much you've slept, craving carbs and sugar like your life depends on it, or feeling flat, tearful, or irritable for no obvious reason. You might want to hibernate, cancel plans, avoid people, and just stay at home under a blanket. Struggling to concentrate or make decisions becomes normal, and you lose interest in things you usually enjoy.

It usually starts around September or October, gets worse through December to February, then lifts when spring arrives. Year after year, the same pattern repeats itself. And if you're thinking "that's just me being lazy in winter," stop right there, because this isn't about willpower or attitude but about actual brain chemistry.

What's happening in your brain

Your brain makes a chemical called serotonin, which helps you feel calm, happy, and balanced. To make serotonin, your body needs sunlight. Less daylight in winter means less serotonin. So, when serotonin drops, everything feels harder. Your mood sinks, your energy disappears, and food becomes the quickest way to feel something good, even if it's just for ten minutes.

That's why you're not craving salad in January. You're craving toast and jam because quick carbs give your brain a brief serotonin boost, as your body is literally trying to fix itself with food. The problem is, it doesn't last, as the crash comes quickly, and then you're back where you started, or worse, feeling guilty on top of everything else.

Ways to support yourself through winter

The good news is your body responds really well to the right support, so you don't have to just grit your teeth and wait for April.

Get outside in natural daylight

Even on grey days, natural daylight is far brighter than indoor lighting. A 20-minute walk in the morning or at lunchtime can make a real difference. You don't need sunshine, just daylight hitting your eyes and skin.

Consider a light box

These aren't just for extreme cases. A light box mimics natural daylight and can help your brain produce more serotonin. You sit near it for about 30 minutes each morning while you have breakfast or a cup of tea. Many people notice a shift within a week or two of starting.

Support your vitamin D levels

In winter, it can be hard to make vitamin D from sunlight in the UK. And low vitamin D affects your mood directly, so consider taking approximately around 1,000 IU daily through the darker months. Liquid forms are easiest to take and absorb well. If you’re unsure about what’s right for you, speak to your GP.

Don't skip omega-3

Your brain is made largely of fat, and it needs omega-3 from oily fish (or supplements) to function properly. This isn't optional for brain health; it's essential. If you're not eating salmon, mackerel, or sardines regularly, consider taking a good-quality fish oil supplement.

Keep your meals regular

When you skip breakfast or go hours without eating, your blood sugar drops, and your mood follows straight after. Eating at roughly the same times each day keeps everything steadier. And always have breakfast, because your brain needs fuel after sleeping all night.

Choose foods that help your body make serotonin

Your body needs certain building blocks to produce serotonin. Foods like eggs, turkey, oats, and dairy contain something called tryptophan, which your body converts into serotonin. Eating these regularly gives your brain what it needs to lift your mood naturally.

Complex carbs like oats, brown rice, and whole-grain bread also help, especially when eaten with protein. They release energy slowly and support stable serotonin levels throughout the day.

On the other hand, too much sugar sends everything on a rollercoaster. You get a quick high followed by a nasty crash that leaves you feeling worse than before.

Watch your evening routine

Bright screens before bed can mess with your sleep hormones. Your brain needs darkness to wind down and prepare for sleep. If you're struggling to sleep, try dimming lights an hour before bed and keeping your phone out of the bedroom.

Also, if you wake in the night, don't switch the light on, as your brain will think it's morning and wake you up properly, making it much harder to get back to sleep.

Consider a natural serotonin boost

There's a supplement called 5-HTP that many people find helpful for SAD. It's a natural precursor to serotonin, which basically means it gives your body the building blocks it needs to make more of this mood-regulating chemical itself. It often also contains B vitamins and zinc, which your body needs for the conversion process to work properly. Magnesium can also help support brain health. 

It’s not suitable for everyone and should not be taken alongside antidepressants. Mild side effects, such as nausea, are sometimes reported. St John’s wort is another supplement people consider for low mood. It’s important to speak to your GP or a qualified health professional before starting either option to ensure it’s safe and appropriate for you.

When to ask for help

If you're recognising yourself in this and it's affecting your daily life (your work, your relationships, your ability to just get through the day), please talk to your GP. SAD is a recognised condition, and there are treatments that work. You don't have to just put up with feeling awful for five months every year.

If you are experiencing thoughts of harming yourself and need urgent help, reach out to someone straight away, whether that's your doctor, a trusted friend, or the Samaritans on 116 123.

You are not making it up

If winter makes you feel like a completely different person, that's real, and it's not just you imagining things. It's not all in your head. The difference between struggling through and actually feeling OK can come down to just a few small targeted changes, such as supporting your serotonin levels, getting proper nutrients into your body, and being kind to yourself about what your body actually needs. This can completely transform how you experience winter. You don't have to wait until spring to feel human again.